For cutoff machining of rare earth sintered magnet blocks (or permanent magnet blocks), various cutting techniques such as outer diameter cutting, inner diameter cutting and wire saw cutting are implemented. Among others, outer-diameter blade cutting wheels are most widely employed. The outer-diameter blade cutting technique has many advantages including less expensive cutting tools, a relatively low cutting allowance associated with cemented carbide blades, a good dimensional accuracy of cut pieces, and a relatively high machining speed. Owing to these advantages and improved mass productivity, the outer-diameter blade cutting technique is widely used in the cutting of rare earth sintered magnet blocks.
Outer-diameter blade cutting wheels for cutting rare earth sintered magnets are disclosed in JP-A H09-174441, JP-A H10-175171, and JP-A H10-175172 as comprising a cemented carbide base having an outer periphery to which diamond or CBN abrasive grains are bonded with phenolic resins, nickel plating or the like. Since the base made of cemented carbide is improved in mechanical strength over prior art alloy tool steel or high-speed steel, there are achieved an improvement in the machining accuracy, an improvement in the yield of pieces due to reduced allowance by the use of thin blades, and a reduction of machining cost due to high-speed machining.
While outer-diameter blade cutting wheels using cemented carbide bases are improved in cutting and working performances over the prior art outer-diameter blade cutting wheels, the market imposes a continuing demand for cost reduction. It would be desirable to have a high-performance cutting wheel capable of machining at a high accuracy and high speed.